The technical field of the invention is that of needleless syringes intended for injection, through the skin, of solid or liquid particles of active principle for therapeutic use.
Specifically, the invention relates, on the one hand, to a needleless syringe functioning on the basis of an initiating device which includes a triggering device associated with a pyrotechnic charge, and, on the other hand, to this triggering device adapted for firing a pyrotechnic charge accommodated in a lightweight object of small size intended to be actuated manually, this object being in particular a needleless syringe.
The solution proposed by the invention recommends the use of a piezoelectric crystal as a central part of the device for triggering the needleless syringe.
It would appear that, in the field of needleless syringes, there is no patent relating to the use of a piezoelectric crystal in the triggering device of such syringes. Mention may be made, however, of European Patent Application EP 0,853,952 which describes an independent initiator casing which can be fitted on needleless syringes and can be used several times. There is merely an allusion made to the fact that this independent initiator casing might possibly include a piezoelectric crystal. In no way, however, does this initiator device form an integral part of the needleless syringe, as underlined by the invention.
By contrast, the use of a piezoelectric crystal for initiating a pyrotechnic charge in objects such as, for example, electrical fuses, blast cartridges or electrical fuse primers is known and is the subject of a number of patents. Reference may be made, inter alia, to French Patent FR 2,665,253 which describes a piezoelectric firing device with resistance wire in a pyrotechnic assembly. This device can be actuated manually by way of a pushbutton with which it is possible to trigger the movement of a weight which is intended to strike the piezoelectric crystal.
The needleless syringes sought by the person skilled in the art must be equipped with a triggering device which can be actuated manually and with which it is possible to do without an activation source which is too energetic or too cumbersome, while at the same time remaining reliable and effective.
The needleless syringe according to the invention meets these requirements.
The subject of the present invention is a needleless syringe provided with an initiating device comprising a triggering device and a pyrotechnic charge, characterized in that the triggering device includes a piezoelectric crystal.
The triggering device advantageously comprises a triggering member connected to a means for impacting the piezoelectric crystal.
The piezoelectric crystal is preferably positioned in the syringe between the impacting means and the pyrotechnic charge to be initiated, and it is inserted in such a way that, during the operation of the syringe, it ensures that the upstream part of the syringe, formed by the triggering member and the impacting means, is leaktight with respect to its downstream part comprising the pyrotechnic charge, the active principle to be injected, and an injection nozzle.
According to a first preferred embodiment of the invention, the impacting means comprises a tongue maintained under elastic stress by being blocked against a stop element, and the triggering member is able to displace said tongue in order to release it, so that it comes to strike the piezoelectric crystal.
The tongue is preferably made of a material having a high degree of elasticity, such as, for example, spring steel or spring bronze.
The tongue advantageously terminates in a weight in order to increase the force of impact on the crystal. This is because the presence of a weight at the end of the tongue will reinforce the action of the lever arm formed by said tongue which is intended to pivot and then strike the crystal at the level of said weight.
The tongue is advantageously integral with the triggering member, so that its displacement before its release is dictated by the movement conferred on the triggering member.
According to a preferred embodiment of the invention, the triggering member is a pushbutton which is intended to be actuated manually and which can slide along an elongate central body, by simple pressure, so as to cause a displacement of the tongue in translation.
The pushbutton is preferably placed at one of the ends of the central body in order to facilitate its actuation, and more especially at the end remote from the injection nozzle.
The central body is preferably hollow and has, on its internal lateral wall, a projection serving as a stop element for the tongue.
The contact surface of the projection against which the weight comes to bear is advantageously plane.
Advantageously, a zone of roughness situated between the pushbutton and the central body makes it possible to increase the frictional forces between these two elements, in the event of the one sliding on the other.
In a preferred manner, the zone of roughness is formed by the mutual engagement of annular protrusions of one of the two elements in grooves provided to receive them in the other element, in such a way as to bring about a minimum level of pressure in order to begin driving the pushbutton home. This precludes any inadvertent triggering caused by insignificant pressure.
The pushbutton preferably has a safety means in the form of a retractable stop element preventing any movement of said button in translation. The other function of this safety means is to protect the end of the syringe through which the active product is to be ejected.
The retractable stop element is advantageously formed by a stopper equipped with a detachable flange, said stopper ensuring protection of the sensitive end of the syringe prior to use, and said flange blocking the pushbutton. A circular line of weakness allows the flange to be separated from the stopper. The flange is rigid and comprises a tab for tearing it off.
According to a second preferred embodiment of the invention, the triggering member is a button which is intended to be actuated manually by rotation about a hollow and elongate central body, in such a way as to cause the rotation of the tongue, said body having, on its internal lateral wall, a projection serving as a stop element for said tongue.
The tongue advantageously terminates in a weight.
The button is preferably placed at one of the ends of the central body in order to facilitate the manual triggering of the syringe.
The rotary button advantageously has a safety means in the form of a retractable ring preventing any rotation of said button.
The retractable ring preferably has a manually accessible tab for tearing off and then removing said ring.
According to a third preferred embodiment of the invention, the impacting means comprises a spring and a weight, and the triggering member is a pushbutton which is intended to be displaced linearly by manual pressure, in such a way as to compress the spring and then release it in order to propel the weight against the piezoelectric crystal.
The spring and the weight are advantageously arranged in an elongate hollow body which serves as a means for guiding them.
The pushbutton preferably has a safety means in the form of a retractable stop element preventing any movement of said button in translation.
The retractable stop element is advantageously formed by a stopper provided with a detachable flange.
In view of what is described for the first preferred embodiment of the invention, the retractable stop element has a dual function: to protect the sensitive end of the syringe and to immobilize the pushbutton.
Finally, the invention concerns a device for triggering a pyrotechnic charge, comprising a triggering member connected to a means for impacting a piezoelectric crystal, said impacting means comprising a tongue maintained under elastic stress by being blocked against a stop element, and the triggering member being able to displace said tongue in order to release it, so that it comes to strike the piezoelectric crystal. The tongue advantageously terminates in a weight in order to increase the force of impact on the crystal. Such a triggering device can, for example, be used for priming grenades. The use of a button which can be actuated by rotation or by pressure is in fact suitable for the priming of grenades to the extent that use of this device is less restrictive than pulling out a pin, especially in a particular situation where the freedom of maneuver of the user is limited, for example when wearing gloves. This device also offers the possibility of priming by means of striking the pushbutton of the grenade hard against an external surface. In general, the triggering device according to the invention, involving the use of a tongue, is adapted to the priming of any type of pyrotechnic charge.
The needleless syringes according to the invention have the advantage of producing a less violent pyrotechnic reaction than that which is observed in the functioning of a percussion primer. Specifically they permit gentle initiation of the pressure-generating composition by way of an electric arc or a spark, and no longer by way of a shock wave.
Moreover, during their triggering and their functioning, they generate an extremely limited sound effect.
Finally, they have the advantage of being placed on the open market without the constraints inherent to devices involving explosives or detonating compositions.